1. Field of the Invention
The present invention generally relates to a rescue circuit of display panel and a rescue method thereof, and in particular to a rescue circuit of display panel and a rescue method thereof that improve resistive-capacitive (RC) delay occurring in a signal line.
2. The Related Arts
FIG. 1 is a schematic view illustrating a conventional way of rescuing a signal line of a liquid crystal display panel. As shown in FIG. 1, the liquid crystal display panel comprises a substrate 10, and a plurality of scan lines 12 and a plurality of signal lines 14 are provided on the substrate 10 with the plurality of scan lines 12 arranged to be parallel to each other and intersecting the plurality of signal lines 14. The scan lines 12 and the signal lines 14 form a plurality of pixel areas therebetween, each being controlled by a thin film transistor (TFT) (not shown) for pixel refreshing. Further, the substrate 10 comprises a scan chip 22 and a plurality of signal chips 24. For clear illustration, only one signal chip 24 is shown in the drawings. The scan chip 22 functions to sequentially drive the scan lines 12, and the signal chips 24 provides the display signal of a pixel to the signal lines 14.
Due to the increase of the number of pixels, the distance between two adjacent scan lines 12 or two adjacent signal lines 14 arranged on the substrate 10 is as small as several micrometers. Consequently, a signal line 14 may get broken and thus open in the manufacturing process due to a foreign object (such as dust). To handle the problem of breaking and thus opening of the signal lines 14, a conventional liquid crystal display panel is further provided with a rescue line 16 on the substrate 10 for repairing a broken signal line. The rescue line 16 is arranged in a peripheral area around a display zone 11 formed by the scan lines 12 and the signal lines 11 and is made intersecting but spaced from the plurality of signal lines 14 by an isolation layer. When it happens that one of the signal lines 14 is broken and thus gets open, the rescue line 16 may be used to recover the portion of the signal line 16 posterior to the opening site through application of laser welding to the intersections (black dot) thereof with the signal line 14. The display signal supplied from the signal chip 24 is transmitted through the rescue line 16, along route 162, to apply to the signal line 14.
Reference is made to FIGS. 1 and 2A. FIG. 2A is a plot of display signals at points A, B of FIG. 1, which are not subjected to correction. A comparison is made between points A, B that are located on the same horizontal line of FIG. 1. This is because a signal line 14 is broken and thus open at point A, and a display signal is transmitted through a rescue line 16, along route 162, to point A; however, the signal line 14 at point B is intact and is not broken, so that a signal may be transmitted along route 142 from the upper side to the lower side. With the increase of the panel size, the numbers of the scan lines 12 and the signal lines 14 are getting increased, making signal transmission along route 162 toward point A is much longer than transmission along route 142 to point B and a correspondingly enlarged resistive-capacitive delay (RC delay). As a consequence, distortion of the display signal at point A is severer than at point B. However, a significant difference of the display signals may lead to the situation that the charging ratio at point A is much smaller than that at point, thus causing a weak line phenomenon around point A.
Reference is made to FIGS. 1 and 2B. FIG. 2B is a plot of display signals of points A, B of FIG. 1 after correction, wherein the display signals at points A, B are respectively shown in phantom lines and solid lines. In the state of the art, a buffer amplifier 20 based circuit is often connected to the rescue line 16 in order to improve the RC delay problem of the signal line around point A, as shown in FIG. 2B. This also solves the weak line problem around point A.
However, as shown in FIGS. 1 and 3, wherein FIG. 3 is a plot of display signals at points C, D of FIG. 1, the display signals at points C, D are respectively shown in solid lines and phantom lines signal. A comparison is made between points C, D that are located at the same horizontal line of FIG. 1. Point C is located at the portion of the signal line 14 anterior to the opening site, while point D is located on a signal line 14 that is intact. Consequently, RC delay at point C is much smaller than that of point D. When the difference of display signals is significant, a weak line phenomenon may similarly occur around point C (due to being of significant difference from the signal line of point D).